High energy particle beam dump and heat sink



Aprifl 25, 1967 E. L. GARWIN ET AL 3,315,732

HIGH ENERGY PARTICLE BEAM DUMP AND HEAT SINK Filed March 29, 1965 4 Sheets-Sheet l INVENTORS EDWARD LGARW/N BY DIETER R WALZ JOSEPH Jwvow ?M Q QLW/ ATTORNEY A R-ii 25, E967 E. L. GARWIN ET AL HIGH ENERGY PARTICLE BEAM DUMP AND HEAT SINK Filed March 29, 1965 4 Sheets-Sheet 2 WM W A O mm M W L R H ND 1 TE w 0 WDJ E ATTORNEY P 25, 1967 E. 1.. GARWIN ET AL HIGH ENERGY PARTICLE BEAM DUMP AND HEAT SINK 4 Sheets-Sheet 3 Filed March 29, 1965 INVENTORS EDWARD L. GARWl/V D/ETER R WALZ JOSEPH JUROW Ami 25, 1967 E L, WW ET AL 3,315,732

HIGH ENERGY PARTICLE-BEAM DUMP AND HEAT SINK Filed March 29, 1965 4 Sheets-Sheet 4 INVENTORS EDWARD L. GARw/N D/ETER R. WALZ JOSEPH Junow ATTORNEY United States Patent ice 3,315,732 HIGH ENERGY PARTICLE BEAM DUMP AND HEAT SINK Edward L. Garwin, Los Altos Hills, and Dieter R. Walz,

and Joseph Jurow, Palo Alto, Calif., assignorsto the United States of America as represented by the United States Atomic Energy Commission Filed Mar. 29, 1965, Ser. No. 443,725 12 Claims. (Cl. 16547) The present invention relates generally to particle beam stoppers and in particular to a particle beam dump utilizing a fluid medium for stopping extremely high energy electron beams, by absorbing the resulting electromagnetic cascade shower and dissipating it as heat into a fluid.

In the performance of high energy physics experiments utilizing high energy particle beams, there is need of devices which are capable of absorbing and dissipating the remaining energy of a particle beam, e.g., after the physics experiments have been performed with the beam, when the accelerator is being adjusted, etc. Such devices must be capable of absorbing likewise a large amount of the radiation resulting from the impingement of the beam thereon to prevent radiation damage to the surrounding structures and minimize exposure hazards to personnel performing the experiments, instrumentation, and the like. Since accelerators generating the high energy beam must operate continuously to avoid excessive down time for repairs, such beam stopping devices must be capable of operating continuously over a period of many years with a minimum of repair and maintenance.

Until the present time, beam stoppers or dumps have comprised simply a block or plurality of blocks of material having a high atomic number and good conductivity, whereby the heat adsorbed from the beam by the blocks is dissipated by air or by the circulation of a fluid coolant in contact with the absorbers. Until recently a more sophisticated beam dump design has not been needed, since beams utilized in performing physics experiments have been of comparatively low energy and power. Recent developments in the accelerator field have led to the design of a two-mile accelerator capable of generating beams having powers of the order of 2.2 megawatts at an energy of 11 billion-electron volts (gev.). Beam stoppers such as briefly described above, wherein the energy of the beam is dumped into a solid block of material, cannot be utilized in conjunction with such high energy accelerators since the energy deposition rate is so high that damage proceeds at a highly destructive rate whereby, it has been ascertained that no more than 7 to 8 pulses would be required to eliectively destroy the device. To further indicate the inability of such beam dumps to meet requirements, the above-mentioned two-mile accelerator is designed to produce 360 pulses per second; obviously, the beam dump would be destroyed in less than 1 of a second. The stopping of high energy beam particle bunches of course results in the production of intense showers of high energy electromagnetic and secondary particle radiation for which weighty shielding must be provided.

The present invention overcomes the above mentioned shortcomings of prior art beam dump devices by providing a beam dump in which the beam is directed into a circulating absorber-coolant fluid wherein the beam is stopped and the energy from the incident beam is dissipated by means of the circulating fluid. The beam dump of the invention is capable of fully absorbing and dissipating, e.g., a particle beam having a beam power of 2.2 megawatts at 11 gev. for prolonged periods of time with a minimum of maintenance and repair. The beam dump of the invention can be utilized in conjunction with circular accelerators in which a beam is extracted as well as linear accelerators, and is adaptable for use not only with 3,315,732 Patented Apr. 25, 1967 electron beams but with various heavier charged particle beams as well.

Accordingly, it is an object of the present invention to provide an accelerated particle beam dump capable of absorbing and dissipating extremely high power particle beams, of the order of, for example, 2.2 megawatts.

It is another object of the present invention to provide a beam dump which utilizes a circulating fluid as a medium for absorbing and dissipating a selected proportion of the beam energy in a high energy particle beam.

It is yet another object of the present invention to provide a beam dump for use in an accelerator switch-yard complex wherein the device is easily handled and situated to permit ready replacement of components thereof, e.g., the window, in the event repairs are necessary.

It is still another object of the present invention to provide a high energy beam dump comprising a structure of straightforward, easily assembled design which can be constructed of easily obtainable materials.

Yet another object of the present invention is to provide a beam dump which utilizes a mass of swirling water for partially absorbing and dissipating a pulsed particle beam of given energy, wherein the circular velocity of the water mass is selected such that consecutive pulses of the beam will strike new increments of water mass.

Still another object of the present invention is to provide a high energy beam dump, not only capable of absorbing and dissipating extreme beam energies but which, due to its configuration, inherently slows and dissipates the secondary particles generated therewithin.

Yet a further object of the present invention is to provide a high energy beam dump which combines a swirling mass of absorber-coolant fluid with a material mass to provide a high energy beam dump of relatively short length.

Other objects and advantages will be apparent in the following description and claims considered together with the accompanying drawings, in which:

FIGURE 1 is a perspective, partially-sectioned view of one embodiment of the present invention exemplifying the configuration and related mechanism thereof.

FIGURE 2 is a cross-section plan view taken along a horizontal plane located slightly above the longitudinal axis of the cylindrical housing of the device of FIGURE 1 FIGURE 3 is a partially-sectioned elevational view of the device of FIGURE 1.

FIGURE 4 is a cross-sectional end view taken along line 4-4 of FIGURE 3.

FIGURE 5 is a cross-sectional end view taken along line 5-5 of FIGURE 3, and showing in greater detail the construction of the baflie assembly.

FIGURE 6 is a top view of the baflie assembly shown in FIGURE 5, taken along the axis of the invention.

The beam dump of the present invention is designed and constructed to utilize the principle, or law, of conservation of angular momentum, i.e., the principle of rotational motion and conservation of momentum of liquid mass rotating within a vessel, i.e., V-r=constant, wherein V is the angular velocity of an increment of the liquid, and r is the radius of rotation of the increment. Due to rotation of the liquid mass normal to the path of the beam at a preselected distance from the vortex thereof, it is provided that successive pulses of the beam impinge upon different increments of the liquid mass. As is known, the impingement of a rapid succession of beam pulses, of sufliciently high energy and power density upon a stationary mass of water will tend to evaporate a portion of the liquid mass, causing a reduction in the density and an associated decrease in the electromagnetic energy absorption characteristics thereof. If such a decrease of electromagnetic energy absorption characteristics were alowed to take place, the beam would tend to pass through he device to impinge upon, and thus destroy by overleating, solid portions of the structure of the device or my structure to the rear of the device. Accordingly, the me at which the water mass is rotated is selected relative o the beam energy, beam power density, beam cross- ;ection and repetition rate of the pulses, such that the :emperature rise of the mass of water upon which the Jeam impinges, is held, for example, generally to within 1 1 or 2 C. temperature rise at the electromagnetic shower maximum produced by impingement of electron pulses or bunches in the beam. With such a limited temperature rise, outgassing of the hydrogen formed in the water due to radiolysis will be minimized and absorption of an initial increment of the incoming beam will be effected by the water mass, thereby preventing any detrimental radiation damage to solid portion of the device structure. Although the present invention is particularly described with reference to the use of water as the fluid medium, it is to be understood that various other coolant fluid mediums, i.e., radiation resistant organic coolants, aqueous solutions and suspensions including radiation absorbers, etc., could be utilized in place of water. Water is herein preferred due to its ease in handling and processing, as well as due to the simplicity of the chemical reactions which occur upon incidence of the beam thereon.

Referring now to FIGURE 1, the beam dump in accordance with the present invention comprises a relatively large, cylindrical, stainless-steel tank 12 constructed to define front and rear chamber sections 14, 16 respectively. The front section 14 comprises essentially a large cylindrical volume in which the above-mentioned Water mass is circulated about the longitudinal axis of the tank 12, i.e., the section 14, and the rear chamber section 16 has a baflie assembly 18 formed of a series of baffle plates 19 disposed in pre-arranged configuration therein. Upon entering section 14, the impinging particle beam bunch, e.g., high energy electrons interact to produce a cascade of high energy electromagnetic radiation, i.e., gamma rays and secondary particles. Complete absorption of all radiation then occurs in chambers 14 and 16.

More particularly, the dimensions of the stainless steel tank 12 are chosen with the purpose of absorbing and dissipating the energy of an incoming beam, herein indicated by an arrow and identity numeral 20, which is introduced thereto at beam output end of an accelerator herein designated by numeral 21. The beam dump tank length may be chosen so that an electron beam 20 with an energy of 20 billion-electron-volt (gev.) is absorbed and rendered harmless within an equivalent length of radiation absorption lengths. For example, the beam dump of the present invention could comprise a single elongated tank of circulating water of an equivalent length of 30 radiation lengths into which the beam is introduced at one end. However, in the interest of saving space the present invention advantageously employs a chamber section 16 which furnishes an equivalent of 20 radiation absorption lengths, utilizing the material of the baffle assembly 18 as well as the water circulating therethrough. In addition, the front chamber section 14 is made, e.g., 10 radiation lengths long, which is enough to allow development of the electromagnetic cascade past its shower maximum and degrade it enough that section 16 can be employed safely. The diameter of the tank 12 is chosen to adequately degrade the diverging radial electromagnetic shower generated by the impingement of the beam 20 upon the swirling water mass. Furthermore, the diameter of the tank 12 is chosen to provide a volume sufiiciently large to partially slow the fast neutrons created by the impinging beam 20 to their thermal energy range, thus facilitating their capture by structural components and neutron absorber poisons incorporated therein if needed.

The beam 20 is introduced to the inner volume of the tank 12 through a beam window assembly 22 disposed 10 in and out of position.

in the front section 14; the window assembly 22 provides means for separating the vacuum environment of the accelerator from the pressurized fluid of the beam dump 10. Water, which is introduced into the rear chamber section 16, is passed through the baffle assembly 18 and thence into the front section 14 in a predetermined flow pattern as is further described infra. It is to be noted that the temperature of the water passing through the beam dump 10 gradually increases as it flows from the rear section 16 towards the front section 14. The direction of the Water flow as it passes from the rear towards the front of the tank 12 serves to protect the front structures of the beam dump 10 by minimizing the probabilities of cavitation erosion. This erosion is generally due to high heat fluxes, highly subcooled liquid, and the mechanism associated with boiling fluid heat transfer.

Water is introduced to the tank 12 by means of an inlet pipe 24 which is connected to the tank 12, and in particular to the rear section 16 at a position along the upper circumference thereof. As shown in FIGURES 1-3, the connection of inlet pipe 24 is located adjacent the end of rear section 16 behind the last baffle plate of the baflie assembly 18. Upon passing through the beam dump 10 in the predetermined flow pattern of above-mention, the water is removed from the tank 12 via an outlet pipe 26. As shown in schematic, inlet pipe 24 and outlet pipe 26 extend from the beam dump 10 to couple to a suitable water distribution and purification system hereinafter termed a primary (radioactive) coolant-fluid system. The primary coolant-fluid system is shown, by Way of example only, as an ion-exchange purification system 28, a heat exchanger system 29, and a fluid pump 30 connected together in series and to the inlet and outlet pipes 24, 26 respectively. Since such primary coolant fluid systems are generally known in the art, no further de scription thereof is herein included.

Various lengths of auxiliary piping and tubes are connected to the beam dump 10 to provide for various additional environmental problems associated with the use of a fluid as a beam-stopping medium. For example, a gas vent pipe 32 is connected to the front section 14 at a point along the topmost wall portion thereof, wherein the pipe is utilized to remove various gases which generally are formed by the radiolysis of the water due to interaction of the beam with the water. The most significant contribution to gas production comes from hydrogen (H formation, but other components such as H+, 0-1 0 (OI- )1 H 0 and H0 are also formed in the aqueous medium.

Since the window disposed in the window assembly 22 is more or less isolated from the water flow patterns circulating in the front section 14, and since heat is generated in the window due to the passage of the beam 20 therethrough, it is necessary to provide extra cooling of the window surface. Accordingly, a window coolant inlet tube 34 is provided between the inlet pipe 24 and the window assembly 22. Likewise, a window coolant outlet tube 36 is coupled from the Window assembly 22 and is connected at its opposite end to the outlet pipe 26. The window inlet and outlet tubes 34, 36 respectively provide for circulation of water through the window assembly 22 with a predetermined flow pattern in a manner described in greater detail hereinafter.

In addition, a tank drain pipe 38 is connected at one end to the lowermost point of the rear section 16 and is utilized to remove all water from the tank 12 at such time as need for such action arises, for example, when repairs or maintenance must be performed on the beam dump 10. Such a drain pipe 38 is necessary to remove the water prior to any work that is done on the dump 10 since the water after extended use is contaminated and highly radioactive.

As shown in FIGURE 1, a tank-support carriage assembly 40 is provided to allow movement of the beam dump The carriage assembly '40 comprises essentially a rectangularly shaped I beam frame assembly 42, having four V-grooved wheels 44 secured at the corners thereof in rotatable relation therewith. The wheels 44 are further adapted to mate with and rotate along suitable lengths of track in the switchyar-d complex of an accelerator facility. Tank support brackets 46 are shaped to conform to the outer circumference of tank 12, and are disposed to connect to, and span across, the axially extending portions of the I beam frame assembly 42, Although the tank-support carriage assembly 40 has been particularly described in conjunction with a single, exemplifying configuration, it is to be understood that any means for supporting the tank 12 in movable relation within the switchyard complex could be utilized. In fact, the support could be a rigid, fixed support mounted in the switchyard complex whereby the tank is removed vertically by means of a crane, thus precluding the need for wheels and/or longitudinal motion.

Referring now to FIGS. 2, 3 and 4, there is shown in greater detail one embodiment of the beam dump exemplifying the preferred construction thereof in accordance with the present invention. As shown, the cylindrical tank 12 is divided to provide front and rear chamber sections 12, 16 respectively, by means of a flat, circular divider plate 48 which is concentrically fitted within the tank 12 and sealed thereto around most of its periphery. An aperture 50 is formed in the plate 48 at a position adjacent to the wall of the tank 12. Aperture 50 receives, and is sealed to, one end of a hollow pipe hereinafter termed an inlet header pipe 52. Header 52 extends axially from the plate 48 and along the wall of tank 12, to terminate at its opposite end near the front end of the front section 14. The frontmost end of the inlet header 52 is sealed by means of a circular steel plate 54. Strut braces 56 are secured at one end to the inlet header 52 and extend downwardly therefrom to secure at their opposite ends to the inner walls of the tank 12, thus providing support for the header 52. A spaced series of holes 58 are formed in the inlet header 52 along the length thereof, wherein the series of hol s are disposed along a plane which passes through a diameter of the header 52 at an angle of 30 with a vertical plane. Although an angle of 30 from the vertical is herein particularly specified for the row of holes 58, same may be disposed from the vertical at other angles, such as in the range of 20 degrees to 35 degrees. The general requirement in positioning the holes 58 is that they are oriented so as to inject the water into the volume of front section 14 in a direction tangential to the circular walls thereof to rotate the coolant mass at the requisite rate mentioned above.

An exit header 60 formed of an elongated length of hollow pipe, similar to that forming the inlet header 52, is coaxially disposed along the central length of chamber 14. The end of the exit header conduit 60 nearest the divider plate 48 is sealed by means of a cap 62 and the opposite end of the header 60 extends coaxially through the front end wall of the front section 14 to connect to the exit pipe 26. The exit header 60 is held in position by means of suitable strut braces 64 which extend therefrom to secure at their opposite ends to the wall of the tank 12, The exit header 60 has formed therein, for example, four rows of spaced holes 66 extending the entire length of the header. The four rows of holes lie along diametric longitudinal planes of header tube 60, with said planes disposed preferably at 45 to a horizontal plane. The planes of the rows of holes could be disposed at other than 45 to the horizontal. Thus water injected from the holes 58 in inlet header 52 into chamber 14 is forced to rotate inwardly towards the centrally-extending exit header 50' to follow thus an involute path herein designated by numeral 67.

Referring again to FIGS. 14, there is shown in somewhat simplified configuration the baflie assembly 18 of previous mention. In general, the baffie assembly 18 is constructed of a series of chrome-plated copper baffle plates 19, which have varying thicknesses and which are spaced apart a predetermined distance as required to effect a predetermined flow rate of water passing through the baffle assembly 18. The bafile plates 19 are disposed to form a generally rectangular box-like configuration, having arcuate upper corners to match the inside circumference of the tank 12. The series of baffle plates 19 is preassembled as a unit and is thereafter secured to the divider plate 48 in a manner further described hereinafter. For reasons of simplicity of presentation, the baffle assembly 18 is herein depicted in FIGS. l-4 with only eight bafile plates, whereas the actual number of plates as well as their thickness is determined by the energy, or more particularly, the particle density of the beam to be stopped, and upon the various dimensions and/ or materials utilized in the construction of the beam dump 10. Thus, thicker plates could be utilized in lower beam current applications, to thus change the ratio of copper-to-water medium in favor of copper. In the present embodiment, the baffle plates generally designated by numeral 19 are secured at their lower end to a baffle support plate 70 which defines the bottom of the generally rectangular box-like configuration of above mention. The batfie plates 19 extend upwardly from the support plate 70 to approach but not quite touch the inside circumference or surface of the portion of tank 12 defined as section 16. To provide a flow path for passage of the water fluid, the series of plates 19 have openings formed alternately therein at their upper and lower extremities. For example, plates numbered 72 have an opening formed along the bottom edge thereof between the plate and the lower support plate 70, while alternate plates numbered 74 have openings formed along the upper edge thereof between the plates and the inside circumference of the rear section 16. Water entering through the opening at the lower end of the last plate 72 is forced upwardly between same and the succeeding plate 74 to pass through the opening at the upper end of the latter, and thence through the lower opening in the next plate 72, and so on through the series of plates. Thus, as shown by arrows 75 depicting the flow path, of the coolant-absorber water is passed alternately above and below successive plates thereby thoroughly mixing the Water while simultaneously presenting different counter current flowing increments of water to successive pulses of the incoming beam. Vertical baffle assembly support plates 76 and 78 are secured in sealed relation to the lateral edges of the series of baffle plates 19 whereby the support plates 76 and 78 define the sides of the box-like configuration of previous mention. The support plates 76, 78 are in turn welded at the ends thereof to the inside surface of the rear section 16 to thus provide further support for the baffle assembly 18. Water baflie strips 80, 82, having tapered ends formed thereon, are secured along their lengths to vertical bafiie assembly support plates 76, 78 respectively. An arcuate flat plate 84 is formed to fit between vertical support plate 76 and the adjacent arcuate portion of the inner circumference of the rear section 16, and is securely sealed around its entire periphery to define thus one wall of an enclosed volume 86. Volume 86 is further defined on the remaining three sides by the curved wall of the tank 12, the vertical support plate 76 and the divider plate 48. Thus it may be seen that the enclosed volume 86 defines in essence a manifold arrangement which provides for counter current passage of water from the battle assembly 18 to the inlet header 52.

In addition to the series of bafiie plates 19 there are provided additional bafile plates which are secured directly to the divider plate 48, and which are particularly designed to accept and withstand the initial contact with the diverging beam upon its passage through the water medium in the front section 14. By way of example only, a flat plate 88 is disposed between the 7 first plate 74 of the baffle assembly 18, and the divider plate 48. Plate 88 has an opening at the bottom edge thereof whereby water flows under plate 88. As shown in the figures, the thickness of the plates is progressively decreased approaching the front of the section 16, and to allow funneling the water from the baffie plate assembly 18 to the inlet header 52 there are provided first and second curved plates 90 and 92 respectively which are disposed to bulge inwardly towards the front section 14. The curved plates 90, 92 are secured along their periphery to the divider plate 48. Second curved plate 92 is sealed at its bottom to the front edge of the lower baffie support plate 70, is sealed at its lateral edges to the divider plate 48, and the upper end thereof has an opening therein to allow water to spill over the upper edge of the plate 92. The lower end of the first curved plate 90 extends below the lower support plate 70 a substantial distance and is sealed to the divider plate 48 by an arcuate strip 94. An aperture 96 is formed in the divider plate 48 immediately below the lower support plate 70 and above the arcuate strip 94. A coupler pipe bent at 90 to form an elbow 98, is secured at one end to divider plate 48 and in particular within the aperture 96. The other end extends at right angles therefrom and is sealed to an aperture 100 formed in the vertical support plane 76. Accordingly, it may be seen that elbow 98 provides a passageway for communicating the volume between the curved plates 90, 92 with the enclosed volume 86. Other equivalent means for tunneling or otherwise passing the water from the outlet of the baffle plate assembly 18 to the inlet header 52 may be utilized in place of the curved baffie plates 90, 92, elbow 98 and enclosed volume 86, herein specifically set forth.

A hollow drain member 102 having a series of radially spaced holes formed therein is secured to the tank 12 with the holes in communication with the wall of the tank 12. The other end of drain member 102 is adapted to connect to the drain pipe 38 via a short length of coupling pipe 104 which is passed in sealed relation through the wall of the tank 12. An upwardly extending drain system such as member 102 is utilized herein rather than a hole formed at the bottom of the tank, to preclude the possibility of any flakes or pieces of material which might be deposited at the bottom of the tank 12 from covering the drain opening, thus rendering the drain system inoperative. Pipe 38 is in turn connected to a suitable pump 106 which is capable of pumping, and thus removing, any water in the beam dump at such time as drainage thereof is necessary.

There are various places in the construction of the baffie plate assembly 18 wherein stagnant pockets are formed, whereby the gases produced by beam incidence with the water may tend to collect. To allow the escape of the gases within such pockets and to further allow a continuous, though, small flow of water through such pockets to prevent also overheating of the surrounding structure, small holes or vents (not shown) may be drilled through the structure, generally located at the top thereof, in communication with such pockets.

Referring now to FIG. 3 and considering the waveguide window assembly 22 of previous mention, same comprises essentially a hollow cylindrical member 108 of generally diverging inner volume, which is sealed within the end wall of front section 14, in generally parallel relation to the axis of the tank 12, and at the spot thereon where the beam is to enter the tank 12. An inner cylindrical sleeve 110 is coaxially disposed within the cylindrical member 108 and is sealed at either end to the respective ends of the member 108. Axially extending dividing strips 112 are disposed along a horizontal plane within the annular volume defined between the sleeve 110 and the diverging inner surface of the cylindrical member 108. The divider strips 112 are sealed to the surrounding members to thus divide the annular volume into two separate volumes; upper volume 114 and lower volume 116.

Oppositely spaced slots 118 are formed in the front end of the sleeve 110 at the top and bottom thereof to provide communication between the volume within sleeve 110 and the upper and lower volumes 114, 116 respectively. A window 120, having a generally spherical cross section, is disposed against the beam-entrance end of the cylindrical member 108, with the outer periphery thereof disposed concentrically against a suitable sealedge configuration, such as a knife-edge, formed on the end of member 108. The adjoining donwstream end of the accelerator 21 is disposed concentrically against the opposite side of the window periphery, and accelerator and member 108 are clamped together by a demountable coupler, e. g., a flange and bolt configuration, to confine the window 120 therebetween. The convex surface of the window 120 faces towards the accelerator 21. A fluid-to-atmosphere seal is effected on the tank 12 side of the window, and a vacuum-to-atrnosphere seal is effected on the accelerator 21 side thereof. To provide for additional cooling of the window 120, water is passed through the window inlet tube 34 (see FIGS. 1 and 2), into the lower volume 116 within the window assembly 22, is forced through the slits 118 past the surface of the window 120, through the opposite slits 118 into the upper volume 114, and from thence into the' exit pipe 26 via the window outlet tube 36.

Referring now to FIGS. 5 and 6, there is shown in greater detail by way of example only, the baffie assembly 18 of previous mention. The assembly 18 comprises more particularly a spaced series of sixteen bafi'le plates 19, disposed within the box-like configuration formed by means of bafile support plates 76, 78 and 70. In addition the baffie assembly 18 utilizes the three additional bafiie plates 88, 90, and 92, the latter plates being mounted directly to the divider plate 48. Plate 88 is a straight fiat plate similar to baffie plates 68 but plates 90 and 92 are curved plates. As shown in FIG. 6 the thickness of the plates increase progressively from front to rear plates according to the exponential attenuation of the cascade shower. Thus the initial beam receiving plates 90 and 92 are extremely thin to limit production therein and to provide greater heat dissipating qualities essential upon initial contact with the beam cascade shower after it passes through the water mass. Due to the thinness of the first plate 90 and the desired curvature thereof it is preferable to provide additional support for the plate 90'. Such support is provided by means of lower and upper plate sup-ort strips 91, 93, which are welded at their lateral ends to the divider plate 48. The plate 90 is then secured as by means of bolts 95 around the entire periphery thereof. Bolts 95 likewise fasten the lateral edges of plates 88 and 92 to divider plate 48, as particularly shown in FIG. 6. The box-like configuration of baffie plates 19, which comprises essentially the major portion of the baffle assembly 18, is secured to the divider plate 48 by means of four steel bolts 97 which extend through the entire series of baflle plates 19 and the divider plate 48 to bolt thereto. The baffie plates 19 are held in spaced-apart relation from one another by means of suitable spacers 99 placed between the plates and through which the bolts 97 are passed.

It is to be understood that although the baflle assembly 18 is herein particularly shown with vertically extending baffle plates 19 having openings therein alternately at the top and bottom ends, various other configurations of baffie plates could be utilized. For example, the baffie plates 19 could be vertically oriented with alternate openings formed in the lateral ends there-of, whereby the flow of water would proceed horizontally back and forth through the array of plates 19. In order to provide an even flow of water through the baffie assembly 18 along the entire vertical height thereof when the plates are so oriented, a greater rate of water flow would be required than is required for the configuration having top and bottom openings, and irreversibilities due to expansion 9 and contraction of the flow passages would increase. Likewise, it is to be understood that any means of supporting the baflle assembly 18, such as for example, variously oriented struts or braces or similar brackets could be utilized in place of the bolts 97 secured to the divider plate 48, and the vertical baffle support plates 76, 78.

In operation, water is introduced by means of inlet pipe 24 to the region of rear section 16 located behind the baffle assembly 18, whereupon it is forced through the baffle plates 19 of the assembly 18 in the manner hereinbefore described and depicted by arrows 75. The water exits from the baffle assembly 18 via the volume between curved plates 90, 92 and from thence through elbow 98 and enclosed volume 86 into inlet header 52. The water is thereupon forced through holes 58 in header 52 and ejected tangentially against the wall of the front section 14. Such tangential injection of water into the tank 12 causes the water mass therewithin to rotate about the axis of the tank 12. The number and diameters of the holes 58 in the header 52 are determined by the required flow rate of water, not only through the baflie assembly 18 but also within the front section 14. The even spacing of the holes 58 along the header 52 provides a preferred uniform flow of water from the header 52 along the entire length of the front section 14 of the tank 12, thus minimizing irreversibilities due to mixing of the cooling fluid.

As previously mentioned, the water injected into the front section 14 exits through the co-axially extending exit header 60 which has a diameter equal to the diameter of the header 52 but which has four rows of holes spaced therealong. Since the volume within the exit header is held at a lower pressure than the pressure of the water within the front section 14, a given mass of water injected into the tank by means of inlet header 52 will progressively approach the exit header 60 while rotating within the cylindrical front section 14, describing thus the inwardly spiraling or involute path 67. The given mass of water finally enters the 4 rows of holes 66 in the exit header 60, whereupon it is removed from the tank 12 via the exit pipe 26; the water is then passed through the water processing and cooling system 30, where the absorbed heat and any undesirable trace of gas and radioactivity in the water is removed. The water is thereupon ready for recycling through the beam dump 10.

The beam window assembly 22 as shown in FIG. 3 is disposed in the front end Wall of the front section 14 approximately midway between the axis and the top of the tank 12. Exact positioning of the window, that is, the exact point at which the beam 20 enters the mass of swirling water within the front section 14 is generally determined by the energy of the incoming beam 20, and is related to the velocity of the mass of water which is passing the window 120. Conversely, the diameter of the tank 12 is determined in part by the beam energy which is to be dumped, by the flow rate of the injected water within the rear and front section 16, 14 respectively, and by the point of incidence of the beam 26 into the water mass within the front section 14. Furthermore, the beam 20 cannot be dumped too close to the wall of the tank 12 since the beam as well as the produced secondary particles diverse outwardly within front section 14, and would pass through the walls of the tank 12, thus creating excessive radiation hazard outside tank 12. On the other hand, if the beam is injected into the tank too close to the axis thereof where the fluid velocity is higher and thus generally preferable, the outlet header 60 would tend to overheat and could be destroyed. The preferred spot for injection of the beam 20 would be generally in the radial midregion between the axis and the top of tank 12, wherein such a locus lies along a line passing through the .midportion of the baflie assembly 18. Accordingly, as the beam diverges upon passing through the water mass in front section 14, its entire cross section will still strike 19 well within the periphery of the series of plates of baffle assembly 18.

The following specifications are set forth as examples of specific parameters which may be employed in the configuration of the present invention in conjunction with a beam dump capable of handling pulsed beams in the power range of 2.2 megawatts at pulse rates of 360 pulses per second. Tank 12 has a diameter of 54 inches, the rear section is 62 inches long and the front section is 148 inches long. The inlet and outlet headers, 52, 60, respectively are formed of 6 inch diameter pipe, as are also inlet pipe 24, exit pipe 36 and elbow 98. Of the order of 560 gal./min. of water is circulated; however, this rate may be varied upwardly or downwardly with other plate spacings and with other copper-water ratios. In any event the rate of circulation is determined to control the incremental temperature rise within the limits set out above. The holes 58 and 66 in headers 52 and 60 respectively are 0.375 inch in diameter; the header 52 having one row of 54 holes equally spaced2 /s-inches apart, while header 60 has 4 rows of 49 holes equally spaced 3 inches apart. The tank 12 and the various pipes, including the headers, are formed of stainless steel material to provide resistance against corrosion. The battle plates 19, 88, and 92 vary in thickness from A; inch to 1 /2 inches the intermediate plates having thicknesses of A4, /8, /4, and 1 inch. The plates are preferably formed of copper material which is first plated with nickel and thereafter plated with hard chrome. The combination of metals provides a preferred heat-absorbing-dissipating medium which deteriorates at a negligible rate in use.

Additionally, the hard chrome surface has the property of tending to decompose H 0 while simultaneously providing greater resistance to heat with a minimum of flaking thereof. The. nickel layer is utilized between the chrome and the copper materials to average out the coefficient of expansion which exists between the two metals at varying temperatures and avoid flaking of the chrome plate. Copper is utilized as the base material since it has a high atomic number compared to other materials suitable for use as plates, and has a relatively high thermal conductivity. The flow rate of coolant fluid is generally dependent upon the spacing existing between the baflle plates 19, and in the particular beam dump 10 herein described, is equal to approximately 550 gallons per minute.

The window 121 is manufactured of copper and is likewise plated with nickel and chrome in the manner of the bafile plates 19. The copper used is generally of the type commonly known as oxygen free high conductivity (OFHC) copper. The window is 50 mils thick, spherical in shape, and is disposed within the window assembly 22 with the convex side thereof facing towards the incoming beam 20. The window is held in place by means of a replaceable bolted vacuum flange (not shown) in an accessible position outside of tank 12 and thus could be easily replaced in case of failure.

While the invention has been disclosed with respect to a single preferred embodiment, it will be apparent to those skilled in the art that numerous variations and modifications may be made within the spirit and scope of the in vention, and thus it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. A beam dump for absorbing and dissipating the energy and radiation of a high energy particle beam comprising;

(a) an elongated enclosed cylindrical vessel defining therein front and rear enclosed chambers;

(b) a bafl'le plate assembly including a series of enclosed spaced parallel plates disposed within said rear chamber, said parallel plates having preselected portions removed therefrom to provide a counter current flow pattern for said fluid medium from an inlet to an outlet thereof;

(c) fluid circulating pipe [means disposed within said front enclosed volume in communication with the outlet of said baflle plate assembly and adapted to circulate said fluid medium within said front chamber in a rotating axially converging flow pattern;

((1) primary coolantfluid circulating means external of said tank interconnecting said rear chamber and said fluid circulating pipe means to circulate said fluid medium through said baflle plate assembly and said front chamber; and

(e) window means disposed to allow axially oriented passage of said high energy particle beam into said front chamber to interact with said fluid in a region disposed along a path effectively within the cross sectional area of said bafile plate assembly.

2. A beam plate in accordance with claim 1 wherein said baffle plate assembly further comprises a multiplicity of vertically extending parallel plates, said plates being bounded along their lateral edges as well as at the bottom by confining plates to define thereby a box-like configuration, wherein alternate plates of said multiplicity of parallel plates have openings formed at the top and bottom ends thereof respectively, wherein said fluid medium introduced into said rear volume is forced alternately under and over said multiplicity of parallel plates at a predetermined flow rate.

3. A beam dump in accordance with claim 2 wherein said multiplicity of plates is formed of copper coated with nickel and hard chrome plating.

4. A beam dump in accordance with claim 1 wherein said fluid circulating pipe means comprises;

(a) an inlet pipe closed at one end and disposed in spaced relation along the tankwall, the other end of said pipe disposed in communication with said baflie plate assembly outlet, said inlet pipe having openings formed therein along its length to provide for injection of water therefrom into said front chamber at an angle effective to cause rotation of the cool-antabsorber therein;

(b) an outlet pipe closed at one end and coaxially disposed within said tank, the other end of said outlet pipe protruding through the front end of said elongated vessel, said outlet pipe having a series of openings formed therein and adapted to receive the water injected into said front chamber via said inlet pipe.

5. A beam dump in accordance with claim 1 wherein said primary coolant-fluid circulating means comprises an ion-exchange purifying system coupled to said front chamber for removing contaminants from said fluid medium upon circulation of the fluid through said tank, a heat exchanger coupled to said ion-exchange purifying means and adapted to dissipate the heat contained in said fluid medium, and a fluid pump connected to said heat exchanger to receive the processed fluid medium and to introduce same into said rear chamber.

6. A beam dump in accordance with claim 1 wherein said window means further comprises a cylindrical member disposed in sealed relation in the front end of said elongated vessel in the region thereon at which the beam is injected into said front chamber, a Window of preselected material disposed in sealed relation within said cylindrical member, said cylindrical member having window coolant means including a series of passageways therein, said passageways being connected to said fluid medium purifying and circulating means whereby a portion of said fluid medium is continuously introduced into said cylindrical member and across the surface of said window to cool same.

7. A beam dump in accordance with claim 6 wherein said window is formed of a copper coated with nickel and hard chrome plating.

8. A beam dump for absorbing and dissipating the energy and radiation of a high-energy particle beam comprising;

(a) an elongated closed cylindrical vessel;

(b) a circular divider plate sealed transversely in said vessel to define front and rear chambers within said vessel, said circular divider plate having a generally rectangular opening formed centrally therein;

(c) a baffle plate assembly disposedwithin said rear chamber including a multiplicity of parallel spaced baflle plates and defining generally an enclosed boxlike configuration, said baffle plate assembly being secured to said circular divider plate in register with said rectangular opening therein, said baflie plates having selected portions removed therefrom to provide a coolant flow pattern for said water medium from an inlet to an outlet thereof;

(d) water passage means including a length of pipe coupled at one end to the outlet of said baflie plate assembly and sealed at the other end to a circular opening in said circular divider plate;

(e) water injection means including a length of pipe secured at one end to said circular opening in said circular divider plate and extending in spaced relation along the wall of said front chamber, said pipe having spaced openings therein along the length thereof to provide uniform injection of water into said front chamber in a direction generally tangential to the wall of said vessel;

(f) water outlet means communicating with said front chamber and disposed in coaxial relation there'within and adapted to receive the water injected into said front enclosed volume via said water injection means;

(g) primary coolant-fluid circulating means coupled at one end to said water outlet means and at the other end thereof to said rear enclosed volume to periodically recycle said water medium through said elongated tank with predetermined flow rate and pressure;

(h) window means disposed at the beam entrance end of said elongated vessel and including a window secured in sealed relation therein, said window means being disposed at a locus on said elongated vessel whereby said incoming beam axially impinges said circulating water medium within said front chamber along a line extending generally centrally through said bafl'le plate assembly within said rear chamber.

9. A beam dump in accordance with claim 8 wherein said baflle plate assembly defining said box-like configuration further comprises;

(a) first and second side-wall baflie plate support members disposed in sealed relation against the lateral edges of said multiplicity of parallel spaced baffle plates to define the sides of said box-like configuration, said side-wall support members being secured along their upper and lower edges to the wall of said tank;

(b) lower baffle plate support member sealed along its lateral edges to said first and second side-wall support members in perpendicular relation thereto, said lower baflle plate support member defining the bottom of said box-like configuration upon which said multiplicity of baflie plates are disposed; wherein alternate plates of said multiplicity of plates have openings formed therein at the top and the bottom ends thereof.

10. A beam dump in accordance with claim 8 wherein the spaced openings within the length of pipe of said Water injecting means are further defined as a multiplicty of equally spaced orifices disposed in a single row, said roW of orifices oriented along a plane extending generally into the volume of the tank within the range of from 20 to 35 of a vertical plane passing through the axis of the pipe; and wherein said water outlet means comprises a length of pipe extending in coaxial relation into the front enclosed volume of said tank, said coaxially extending pipe having a plurality of rows of equally spaced orifices formed in the wall thereof, said plurality of rows lying along substantially perpendicular planes passing through the axis of the pipe.

11. A beam dump in accordance with claim 8 wherein said water from said ion-exchange and heat exchanger 1 systems and into said rear enclosed volume via an inlet pipe connected therebetween.

12. A beam dump in accordance with claim 8 wherein said multiplicty of spaced parallel bafile plates vary in thickness from approximately A1 inch to 1% inches be- 14 ginning with the front plate and progressing towards the rear plate.

References Cited by the Applicant UNITED STATES PATENTS 1,271,790 7/1918 Snelling 250-48 X 2,429,217 10/1947 Brasch 25049.5 X 2,722,620 11/1950 Gale 25049.5 X 2,899,556 8/1959 Schopper et a1 25049.5 2,900,542 8/1959 McEven 31332 X 3,016,463 1/1962 Needham 250108 3,115,450 12/1963 Schanz 204193.2

ROBERT A. OLEARY, Primary Examiner. A. W. DAVIS, JR., Assistant Examiner. 

1. A BEAM DUMP FOR ABSORBING AND DISSIPATING THE ENERGY AND RADIATION OF A HIGH ENERGY PARTICLE BEAM COMPRISING; (A) AN ELONGATED ENCLOSED CYLINDRICAL VESSEL DEFINING THEREIN FRONT AND REAR ENCLOSED CHAMBERS; (B) A BAFFLE PLATE ASSEMBLY INCLUDING A SERIES OF ENCLOSED SPACED PARALLEL PLATES DISPOSED WITIN SAID REAR CHAMBER, SAID PARALLEL PLATES HAVING PRESELECTED PORTIONS REMOVED THEREFROM TO PROVIDE A COUNTER CURRENT FLOW PATTERN FOR SAID FLUID MEDIUM FROM AN INLET TO AN OUTLET THEREOF; (C) FLUID CIRCULATING PIPE MEANS DISPOSED WITHIN SAID FRONT ENCLOSED VOLUME IN COMMUNICATION WITH THE OUTLET OF SAID BAFFLE PLATE ASSEMBLY AND ADAPTED TO CIRCULATE SAID FLUID MEDIUM WITHIN SAID FRONT CHAMBER IN A ROTATING AXIALLY CONVERGING FLOW PATTERN; (D) PRIMARY COOLANT-FLUID CIRCULATING MEANS EXTERNAL OF SAID TANK INTERCONNECTING SAID REAR CHAMBER AND SAID FLUID CIRCULATING PIPE MEANS TO CIRCULATE SAID FLUID MEDIUM THROUGH SAID BAFFLE PLATE ASSEMBLY AND SAID FRONT CHAMBER; AND (E) WINDOW MEANS DISPOSED TO ALLOW AXIALLY ORIENTED PASSAGE OF SAID HIGH ENERGY PARTICLE BEAMSS INTO SAID FRONT CHAMBER TO INTERACT WITH SAID FLUID IN A REGION DISPOSED ALONG A PATH EFFECTIVELY WITHIN THE CROSS SECTIONAL AREA OF SAID BAFFLE PLATE ASSEMBLY. 